#include <vector>
#include <list>
#include <map>
#include <set>
#include <deque>
#include <stack>
#include <queue>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <string>
#include <cstring>
#include <ctime>

using namespace std;

typedef long long ll;
typedef unsigned long long ull;

static const double EPS = 1e-8;
static const double PI = 4.0 * atan(1.0);
static const double PI2 = 8.0 * atan(1.0);

#define REP(i,n)	for(int i=0;i<(int)n;++i)
#define ALL(c)		(c).begin(),(c).end()
#define CLEAR(v)	memset(v,0,sizeof(v))
#define MP(a,b)		make_pair((a),(b))
#define ABS(a)		((a)>0?(a):-(a))
#define FOR(i,s,n)	for(int i=s;i<(int)n;++i)

int N, K;
int s[50], b[51];

int main(int argc, char **argv) {
	cin >> N >> K;
	REP(i, N) {
		char temp;
		cin >> temp;
		s[i] = temp - '0';
	}
	int b1 = 0, a = 0;
	REP(i, N) {
		if (i >= K) {
			cout << b1 << endl;
			return 0;
		}
		if (a >= 1) --a;
		else ++b1;
		a += s[i];
	}
	int b2 = 0;
	REP(i, N) {
		b[i] = b2;
		if (a >= 1) --a;
		else ++b2;
		a += s[i];
	}
	b[N] = b2;
	cout << (b1 + (K / N - 1) * b2 + b[K % N]) << endl;
	return 0;
}